The present invention concerns a method for arranging a plurality of line filaments above the grid electrode supported on the base plate of a conventional fluorescent tube.
A fluorescent displaying tube, as shown in FIG. 2, comprises a plurality of segmental electrodes A coated with a phophor layer and supported on a base plate B, a grid electrode C above the segmental electrodes A, a filament D above the grid electrode, and a transparent vessel E for containing sealingly all the above elements. The grid electrode C and the filament D are respectively supported by separate supports F and G with a space between them and the other elements. In this case, while the grid electrode C is made of relatively strong material, the filament D comprises a plurality of slender iron wires coated with a carbonate, which must be carefully handled.
Conventionally, the grid electrode C is firstly mounted on the base plate B, and then, a pair of supports G and G' are properly mounted on the base plate B. A plurality of wire filaments D are arranged paralled to each other between said pair of supports G, G' with their ends welded to the supports. During the process, the wire filaments D will be easily bent, and vibrated so as to separate the carbonate thereon. Subsequently, the separated carbonate particles fall on the phosphor layers of the segmental electrodes A through the grid electrode C, thereby impairing the brightness of the phosphor light emitting.